Santa Cruz News - 8 Jun 09

Mercury Found in Coastal Groundwater

By Curtis Cartier
Monday, June 8, 2009

Elkhorn Slough was one of two sites where UCSC researchers
say they found high levels of mercury in the
groundwater.

Scientists at UCSC have discovered high levels of an
ultra-toxic form of mercury in the groundwater of two coastal sites in
California. The groundwater flows, they say, show a previously unknown
source for what have been mysteriously high levels of mercury recently
found in marine environments and in seafood.

"The big question for public health is, 'Where is all
the mercury in seafood coming from?'" says Russell Flegal, professor of
environmental toxicology at UCSC and a coauthor of the study. "What we
have shown is that methylmercury is coming from groundwater in
California at surprisingly high levels."

Sites at Stinson Beach in Marin County and Elkhorn
Slough in Monterey County were found to have the high methylmercury
levels. Methylmercury is a deadly form of mercury that usually shows up
in the ocean food chain and on dinner tables worldwide. Mercury usually
enters the environment through a process called deposition, in which
airborne particles of the element float down to earth. According to the
university, the amount of mercury that falls from the sky in this
fashion has tripled since the industrial revolution 200 years ago.

The levels of mercury found in the two groundwater
sites have a roughly equal amount of mercury as what normally rains down
through the atmosphere, the researchers say. But while humans and their
fossil fuel burning habits are primarily blamed for the increase in
airborne mercury, the study's lead author Frank Black says the natural
weathering of mercury-containing rocks is likely behind much of the
heightened groundwater mercury levels.

"People have assumed that methylmercury must
come from the bottom of the ocean or from surface waters flowing to the
coast," said UCSC biogeochemist Adina Paytan, a coauthor of the
study. "But never from groundwater."